Southern San Juan
AvalancheChris Bilbrey · Nov 26, 2023 · Southern San Juan
Weather
Beautiful sunny day with a light breeze. Single digit temperatures in the morning struggled to warm into the teens, low-20s by the afternoon.
Snowpack
The last two storms flipped the snowpack script in the La Plata Mountains from fall-time hiking/ biking conditions to late-fall backcountry skiing conditions. We found 12 to 16 inches of recent storm snow along the valley bottom up to just shy of 10,000 feet. As we approached 11,000 feet, we found 18 to 22 inches of recent storm snow. The storm snow fell "right-side-up" and was supportive to over-the-snow travel. This area sat below the "meaningful" snow line during early-season storms and is almost entirely void of October hold-over snow. In this area, only the steepest, heavily shaded slopes above 11,000 feet might still harbor a skiff. Cold temperatures and shallow snow depths have helped snow layers facet - albeit at a somewhat slower rate than observed in other places. We found faceted snow grains in the bottom 10 to 15 cm between 0.5-1.5 mm in size. This layer was 4F- on northerly slopes and 4F on east-facing slopes below treeline. This layer produced mixed results in Compression Test (CT) and Extended Column Test (ECT). The kicker appears to be where this layer is less than about 10 cm, it may not be thick enough to support slab failure at present (ECTN 22). Where this layer was around 10 cm or thicker, we observed failures while isolating the column of snow in both CTs and ECTs. The challenge is knowing which slopes, and where on the slope this layer is thick enough. Additionally, the top 3 to 5 cm (in some locations 10 cm) of the snowpack is faceting too, but these grains were smaller (0.5-1.0 mm). Surface hoar formation was abundant in valley bottoms and wind-sheltered areas, and feather growth ranged 3 to 5 mm.
Avalanche
None observed